US20190315434A1 - Bicycle sprocket and bicycle sprocket assembly - Google Patents
Bicycle sprocket and bicycle sprocket assembly Download PDFInfo
- Publication number
- US20190315434A1 US20190315434A1 US16/455,507 US201916455507A US2019315434A1 US 20190315434 A1 US20190315434 A1 US 20190315434A1 US 201916455507 A US201916455507 A US 201916455507A US 2019315434 A1 US2019315434 A1 US 2019315434A1
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- United States
- Prior art keywords
- tooth
- sprocket
- teeth
- axial
- bicycle
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M9/00—Transmissions characterised by use of an endless chain, belt, or the like
- B62M9/04—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio
- B62M9/06—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like
- B62M9/10—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like involving different-sized wheels, e.g. rear sprocket chain wheels selectively engaged by the chain, belt, or the like
- B62M9/105—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like involving different-sized wheels, e.g. rear sprocket chain wheels selectively engaged by the chain, belt, or the like involving front sprocket chain-wheels engaged by the chain, belt or the like
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K1/00—Making machine elements
- B21K1/28—Making machine elements wheels; discs
- B21K1/30—Making machine elements wheels; discs with gear-teeth
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K23/00—Making other articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M9/00—Transmissions characterised by use of an endless chain, belt, or the like
- B62M9/02—Transmissions characterised by use of an endless chain, belt, or the like of unchangeable ratio
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M9/00—Transmissions characterised by use of an endless chain, belt, or the like
- B62M9/04—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio
- B62M9/06—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M9/00—Transmissions characterised by use of an endless chain, belt, or the like
- B62M9/04—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio
- B62M9/06—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like
- B62M9/10—Transmissions characterised by use of an endless chain, belt, or the like of changeable ratio using a single chain, belt, or the like involving different-sized wheels, e.g. rear sprocket chain wheels selectively engaged by the chain, belt, or the like
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
- F16H55/02—Toothed members; Worms
- F16H55/30—Chain-wheels
Definitions
- the present invention generally relates to a method of making a bicycle sprocket and a bicycle sprocket assembly.
- a conventional bicycle sprocket is provided to both a crank assembly and a rear wheel.
- a chain is engaged with the sprocket of the crank assembly and the sprocket of the rear wheel. Accordingly, the rotation of the crank assembly is transmitted to the rear wheel via the chain.
- inner link plates and outer link plates are alternately coupled together to form a continuous loop. Further, the space between a pair of inner link plates facing each other is formed to be smaller than the space between a pair of outer link plates facing each other. Accordingly, if the sprocket teeth are formed so that the thickness (engaging width) of all of the sprocket teeth are the same, the gap between the outer link plates and the sprocket teeth will be larger than the gap between the inner link plates and the sprocket teeth, in the thickness direction of the sprocket.
- a bicycle sprocket is provided with a first tooth and a second tooth in which the axial thickness or width of the first teeth is different from the axial thickness or width of the second tooth for increasing a chain holding force between the first and second teeth and the chain.
- the thickness of the teeth that engage the outer link plates is made larger than the thickness of the teeth that engage the inner link plates by cutting the teeth that engage the inner link plates (for example, refer to U.S. Patent Application Publication No. 2013/0139642, paragraph [0045]).
- the present invention was developed in light of the above-described problem, and one object of the present invention is to provide a bicycle sprocket having high chain holding force and excellent productivity. Further, an object of the present invention is to provide a bicycle sprocket assembly having high chain holding force and excellent productivity.
- a method of making a bicycle sprocket having a rotational center axis comprising providing an annular portion and forming a first tooth and a second tooth.
- the annular portion is made of a base material and has a plurality of teeth integrally formed on an outer perimeter of the annular portion. At least one of the plurality of teeth is processed to form the first tooth, and at least one other of the plurality of teeth is processed to form the second tooth.
- the first tooth is formed to have a first axial chain engaging width that is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link coupled to the outer link.
- the second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing.
- the second tooth being formed by deforming the base material.
- the first axial chain engaging width of the first tooth is smaller than the first axial spacing in the outer link, and larger than the second axial spacing in the inner link. Further, the second axial chain engaging width of the second tooth is smaller than the second axial spacing. Accordingly, the chain can be held securely by the sprocket. Further, since the second tooth is formed by deformation of the material, the productivity of the sprocket can be improved compared to that of the prior art.
- the method of making a bicycle sprocket includes forming a recess in the first tooth, the recess being configured to minimize interference with the inner link. In this way, even if the first tooth is disposed between the outer link, excessive interference with the inner link can be avoided by the recess.
- the method of making a bicycle sprocket includes forming the recess and the second tooth together by the press working. Since the recess and the second tooth are formed together by press working, the productivity of bicycle sprocket can be improved.
- the method of making a bicycle sprocket includes forming four of the recesses in the first tooth such that the first tooth has a plus-sign shape when viewed from a radially outer side.
- the first tooth can be even more reliably prevented from interfering with the inner link of the bicycle chain.
- the method of making a bicycle sprocket includes forming the four recesses and the second tooth together by the press working. In this way, by forming the four recesses and the second tooth together by press working, the first tooth can be even more reliably prevented from interfering with the inner link of the bicycle chain while also improving the productivity of the bicycle sprocket.
- the method of making a bicycle sprocket includes forming the second tooth using a first press working step, a cutting step performed after the first press working step, and a second press working step performed after the cutting step. In this way, the second tooth can be formed reliably and accurately.
- the first press working step includes pressing one axial side of the second tooth and forming a protrusion on an opposite axial side of the second tooth
- the cutting step includes cutting the protrusion
- the second press working step includes pressing the opposite axial side of the second tooth to achieve the second axial chain engaging width
- a method of making a bicycle sprocket having a rotational center axis comprises providing an annular portion and forming a first tooth and a second tooth.
- the annular portion is made of a base material having a plurality of teeth integrally formed on an outer perimeter of the annular portion. At least one of the plurality of teeth is processed to form the first tooth, and at least one other of the plurality of teeth is processed to form the second tooth.
- the first tooth is formed to have a maximum axial width smaller than a first axial chain engaging width, which is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link coupled to the outer link.
- first tooth has a plus-sign shape when viewed from a radially outer side.
- a first additional portion is attached to the first tooth to expand the maximum axial width of the first tooth to the first axial chain engaging width.
- the second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing.
- the second tooth is formed by deforming the base material.
- the first axial chain engaging width of the first tooth is smaller than the first axial spacing in the outer link, and larger than the second axial spacing in the inner link.
- the second axial chain engaging width of the second tooth is smaller than the second axial spacing. Accordingly, the chain can be held securely by the sprocket. Further, since the second tooth is formed by deformation of the material, the productivity of the sprocket can be improved compared to that of the prior art.
- the material of the additional portion can be chosen freely by attaching the additional portion to the main body portion.
- the method of making a bicycle sprocket includes forming the four recesses in the fourth tooth and forming the second tooth together by the press working. Since the recess and the second tooth are formed together by press working, the productivity of bicycle sprocket can be improved.
- a bicycle sprocket having high chain holding force and excellent productivity can be provided. Further, a bicycle sprocket assembly having high chain holding force and excellent productivity can be provided.
- FIG. 1 is a front side elevational view of a bicycle crank assembly in accordance with first and second embodiments.
- FIG. 2 is a front side oblique view of the first sprocket of the bicycle crank assembly illustrated in FIG. 1 according to the first embodiment.
- FIG. 3 is a rear side elevational view of the first sprocket according to the first embodiment.
- FIG. 4 is a partial rear side oblique view of the first and second sprockets according to the first embodiment.
- FIG. 5 is a partial edge view of the first sprocket and the second sprocket according to the first embodiment, as seen from a radially outer side direction.
- FIG. 6 is a front side oblique view of the second sprocket according to the first embodiment.
- FIG. 7 is a cross-sectional view corresponding to the first tooth of the first sprocket and the third tooth of the second sprocket according to the second embodiment.
- FIG. 8 is a front side view corresponding to the first tooth of the first sprocket and the third tooth of the second sprocket according to another embodiment of the present invention.
- FIG. 9 is a partial front side view of the teeth portion of the first and second sprockets according to another embodiment.
- FIG. 10 is a partial edge view of the teeth portion of the first and second sprockets according to another embodiment, as seen from a radially outer side direction.
- FIG. 11 is a front side elevational view of the first sprocket according to another embodiment.
- FIG. 12A is a front side elevational view of the first sprocket according to another embodiment.
- FIG. 12B is a partial cross-sectional view of the first sprocket illustrated in FIG. 12A .
- FIG. 13 is a schematic diagram illustrating a forming state of the second tooth and the fourth tooth according to another embodiment.
- crank assembly 10 (hereinafter referred to as crank assembly) is illustrated in accordance with a first embodiment.
- the bicycle crank assembly 10 basically comprises a crank arm 12 , a first sprocket 14 (an example of a bicycle sprocket), and a second sprocket 16 (an example of a bicycle sprocket). Further, the first sprocket 14 and the second sprocket 16 are examples of a bicycle sprocket assembly.
- the first sprocket 14 and the second sprocket 16 are front sprockets that are configured to engage with a bicycle chain 2 .
- the second sprocket 16 has fewer teeth than the first sprocket 14 .
- the bicycle chain 2 comprises a plurality of pairs of outer link plates 2 a , a plurality of pairs of inner link plates 2 b and a plurality of chain rollers 2 c .
- the chain rollers 2 c couple adjacent pairs of the outer link plates 2 a and the inner link plates 2 b.
- the crank arm 12 is integrally and non-rotatably coupled to a crankshaft 19 .
- the crank arm 12 comprises a sprocket attaching portion 20 and an arm portion 22 .
- the arm portion 22 is non-rotatably with respect to the sprocket attaching portion 20 .
- the arm portion 22 is provided integrally with the sprocket attaching portion 20 as a non-separable member, or separately detachable from the sprocket attaching portion 20 .
- the sprocket attaching portion 20 comprises a plurality (for example, four) of sprocket attaching arms 24 .
- the sprocket attaching arms 24 are disposed in the circumferential direction with spaces therebetween.
- the intervals of the sprocket attaching arms 24 in the circumferential direction are regular intervals.
- an example is shown of a case in which the intervals of the sprocket attaching arms 24 in the circumferential direction are regular intervals, but the intervals of the sprocket attaching arms 24 in the circumferential direction can be irregular intervals.
- Each of the sprocket attaching arms 24 comprises a first attaching portion 24 a and a second attaching portion 24 b .
- the first attaching portions 24 a are configured for attaching the first sprocket 14 .
- the first attaching portions 24 a are formed on distal end portions of the sprocket attaching arms 24 .
- Each of the first attaching portions 24 a is, for example, a through-hole.
- the first sprocket 14 is fixed to the first attaching portions 24 a.
- the second attaching portions 24 b are configured for attaching the second sprocket 16 .
- the second attaching portions 24 b are formed on proximal end portions of the sprocket attaching arms 24 , radially inward from the first attaching portions 24 a .
- the second attaching portions 24 b are, for example, blind screw holes.
- the second sprocket 16 is fixed to the second attaching portions 24 b.
- the arm portion 22 is provided integrally with or separately from the sprocket attaching portion 20 .
- the arm portion 22 is formed integrally with the sprocket attaching portion 20 .
- a pedal attaching portion 22 a is provided on the distal end portion of the arm portion 22 .
- a pedal (not shown) can be mounted to the pedal attaching portion 22 a .
- a coupling hole 22 b is provided to the proximal end portion of the arm portion 22 .
- the crankshaft 19 is integrally and non-rotatably coupled to the coupling hole 22 b.
- the first sprocket 14 comprises a rotational center axis X.
- the first sprocket 14 comprises a first sprocket body 30 (an example of a main body portion), a first annular portion 31 (an example of an annular portion), a plurality of teeth 32 (an example of a first tooth portion and a second tooth portion), and a pair of first shift regions 34 (refer to FIGS. 3 and 4 ; an example of a shift region).
- the first sprocket body 30 is non-metallic, and made of synthetic resin such as carbon fiber-reinforced resin.
- the first sprocket body 30 is formed integrally with the first annular portion 31 .
- the first sprocket body 30 comprises a plurality (for example, four) of first fixing portions 30 a .
- the plurality of first fixing portions 30 a are disposed in the circumferential direction with spaces therebetween.
- Each of the first fixing portions 30 a is, for example, a through-hole. Each of the first fixing portions 30 a is disposed in an opposing position relative to each of the first attaching portions 24 a .
- a first fixing bolt 26 (refer to FIG. 1 ) is inserted through each of the first fixing portion 30 a and each of the first attaching portion 24 a , and is screwed to a nut member (not shown). With this, the first sprocket body 30 is non-movably fixed to the sprocket attaching arms 24 .
- the first annular portion 31 is attached to the first sprocket body 30 . Specifically, the first annular portion 31 is attached to the outer perimeter of the first sprocket body 30 .
- the first annular portion 31 is made of metal, such as aluminum, titanium, or iron/stainless steel.
- a plurality of teeth 32 are formed on the outer perimeter of the first annular portion 31 .
- the plurality of teeth 32 include a first tooth 32 a and a second tooth 32 b as described below.
- the plurality of teeth 32 are provided to the outer perimeter of the first annular portion 31 .
- the plurality of teeth 32 (for example, from a total number of 30 to 60) are disposed side-by-side in the circumferential direction on the outer perimeter of the first annular portion 31 .
- the teeth 32 are formed integrally with the outer perimeter portion of the first annular portion 31 .
- the plurality of teeth 32 are made of metal, such as aluminum, titanium, or, iron/stainless steel.
- the plurality of teeth 32 comprise a plurality of the first teeth 32 a (an example of a first tooth) and a plurality of the second teeth 32 b (an example of a second tooth).
- the first tooth 32 a and the second tooth 32 b are disposed alternately in the circumferential direction, that is, side-by-side in the circumferential direction.
- the first tooth 32 a is formed to be engageable with the outer link plates 2 a . Specifically, the first tooth 32 a is formed to be engageable between the pairs of the outer link plates 2 a in the axial direction.
- the first tooth 32 a is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side.
- the axial direction includes the direction in which the rotational center axis X extends, and the directions that are parallel to the rotational center axis X.
- the axial direction used here corresponds to the directions that are parallel to the rotational center axis X.
- the first tooth 32 a preferably comprises a first recess 32 e (an example of a recess).
- the first recesses 32 e are provided to each corner portion of the first tooth 32 a .
- the surfaces of the first recesses 32 e that are located on the first side surface 14 a are preferably flush with the surfaces of the second tooth 32 b on the first side surface 14 a .
- the surfaces of the first recesses 32 e on the second side surface 14 b are preferably flush with the surfaces of the second tooth 32 b on the second side surface 14 b.
- the first side surface 14 a (refer to FIG. 1 ) is the front side surface of the crank assembly 10 when mounted on the bicycle.
- the first side surface 14 a is an outwardly facing side surface that faces axially outward away from the bicycle frame.
- the second side surface 14 b (refer to FIGS. 3 and 4 ) is the rear side surface of the crank assembly 10 when mounted on the bicycle.
- the second side surface 14 b is an inwardly facing side surface that faces axially inward towards the bicycle frame.
- the second side surface 14 b is located closer to the bicycle frame than is the first side surface 14 a when the crank assembly 10 is mounted on the bicycle.
- the first recesses 32 e are formed by press working, such as forging.
- press working such as forging.
- an example is shown of a case in which the first recesses 32 e are formed by press working.
- the first recesses 32 e can also be formed by cutting.
- the first recesses 32 e are formed to face the end portion of the inner link plate 2 b to minimize interference between the first teeth 32 a and the inner link plates 2 b . In this way, excessive interference between the first tooth 32 a and the inner link plates 2 b can be avoided by the first recesses 32 e . Further, as shown in FIGS. 2, 4 and 5 , by providing the first recesses 32 e to the first tooth 32 a , the first tooth 32 a (excluding the first tooth 32 a 1 and the first tooth 32 a 2 which are for gear shifting) are formed in a substantially + (plus sign) shape, seen from a radially outer side.
- the plurality of first teeth 32 a comprises a plurality (for example, two) of first teeth 32 a 1 configured for gear shifting, and a plurality (for example, two) of first teeth 32 a 2 configured for gear shifting.
- the first tooth 32 a 1 is configured for downshifting in which the chain 2 moves from the first sprocket 14 to the second sprocket 16 .
- the first tooth 32 a 2 is configured for upshifting in which the chain 2 moves from the second sprocket 16 to the first sprocket 14 .
- the first tooth 32 a 1 and the first tooth 32 a 2 are preferably formed in a substantially T-shape, when seen from a radially outer side, by being provided with the first recesses 32 e as described above.
- the first teeth 32 a comprise a first maximum axial width W 1 (an example of a first axial chain engaging width).
- the first maximum axial width W 1 is the axial width in of the portion where the dimension of the first tooth 32 a is the longest in the axial direction.
- the first maximum axial width W 1 is smaller than a first axial spacing L 1 in the pairs of the outer link plates 2 a .
- the first maximum axial width W 1 is larger than a second axial spacing L 2 in the pairs of the inner link plates 2 b.
- the first axial spacing L 1 is the space in the axial direction between the surfaces that face each other of a pair of the outer link plates 2 a .
- the second axial spacing L 2 is the space in the axial direction between the surfaces that face each other of a pair of the inner link plates 2 b.
- the second tooth 32 b is formed to be engageable with the inner link plates 2 b .
- the second tooth 32 b is formed to be engageable between the pairs of the inner link plates 2 b in the axial direction.
- the second tooth 32 b is preferably formed in a substantially ⁇ (minus sign) shape, as seen from a radially outer side.
- the second tooth 32 b is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side.
- the second tooth 32 b comprises a second maximum axial width W 2 (an example of a second axial chain engaging width).
- the second maximum axial width W 2 is the axial width of the portion where the dimension of the second tooth 32 b is the longest in the axial direction.
- the second maximum axial width W 2 is smaller than the second axial spacing L 2 described above.
- the second maximum axial width W 2 is smaller than the first maximum axial width W 1 .
- the second tooth 32 b is formed by processing the second tooth 32 b in the following way, thereby obtaining the above configuration.
- the second tooth 32 b is formed by deformation of the base material of the teeth 32 .
- the second tooth 32 b is formed by press working.
- the second tooth 32 b is formed by forging.
- the second tooth 32 b is formed together with the first recesses 32 e by forging.
- the second maximum axial width W 2 of the second tooth 32 b is set by press working, for example, forging the second tooth 32 b in this way.
- the first shift regions 34 are provided for gear shifting the chain 2 .
- the first shift regions 34 are the regions in which the chain 2 engages with the teeth 32 of the first sprocket 14 during an upshifting operation from the second sprocket 16 to the first sprocket 14 .
- the first shift regions 34 are the regions in which the chain engages with the teeth 32 of the first sprocket 14 during a downshifting operation from the first sprocket 14 to the second sprocket 16 .
- each of the first shift regions 34 comprises a plurality of the first shifting teeth 32 c .
- the plurality (for example, two) of the first teeth 32 a 1 for gear shifting correspond to the first shifting teeth 32 c .
- the two of the second teeth 32 b adjacent to each of the first shifting teeth 32 a 1 for gear shifting correspond to the first shifting teeth 32 c.
- the first shifting teeth 32 c comprise a first guide surface 32 d .
- the first guide surface 32 d is a surface for guiding the chain 2 .
- the first guide surface 32 d is provided to the first shifting teeth 32 c , on the side of the first surface 14 a (refer to FIG. 2 ) or on the side of the second surface 14 b (refer to FIGS. 3 and 4 ) of the first sprocket 14 .
- the first guide surface 32 d is formed concavely, so that the thickness thereof gradually becomes thinner towards the side portion of the first shifting teeth 32 c.
- each of the first shift regions 34 preferably comprises a first protrusion 36 a and a second protrusion 36 b .
- the first protrusions 36 a and the second protrusions 36 b are provided to the first sprocket body 30 , and are configured to support the chain 2 during shifting operation.
- a first pair of the first and second protrusions 36 a and 36 b is circumferentially spaced from a second pair of the first and second protrusions 36 a and 36 b in the circumferential direction of the first sprocket 14 .
- the first protrusions 36 a are protrudingly provided on the second side surface 14 b of the first sprocket body 30 , for guiding the chain 2 to the teeth 32 of the first sprocket 14 .
- the first protrusions 36 a guide the chain 2 to the second tooth 32 b shown by the hatching in FIG. 3 .
- the second protrusions 36 b are protrudingly provided on the second side surface 14 b of the first sprocket body 30 , for guiding the chain 2 to the first protrusions 36 a.
- each of the first shift regions 34 comprises a stepped portion 38 .
- the stepped portions 38 are for facilitating the engagement of the chain 2 , which is supported by one of the first protrusions 36 a , with the teeth 32 of the first sprocket 14 .
- the stepped portions 38 are provided on the first side surface 14 a , radially inward from the tooth-bottoms of the plurality of teeth 32 . Further, the stepped portions 38 are provided to the downstream side in the forward rotation direction R from the first protrusion 36 a .
- the stepped portions 38 are concavely formed in a substantially triangular shape.
- the second sprocket 16 comprises a rotational center axis Y.
- the rotational center axis Y and the rotational center axis X are concentric.
- the second sprocket 16 comprises a second sprocket body 40 (an example of a main body portion), a second annular portion 41 (an example of an annular portion), a plurality of teeth 42 (an example of a first tooth portion and a second tooth portion), and a pair of second shift regions 44 (an example of a shift region).
- the second sprocket body 40 is made of metal, such as aluminum, titanium, or iron/stainless steel.
- the second sprocket body 40 comprises a plurality (for example, four) of second fixing portions 40 a .
- the second fixing portions 40 a are disposed in the circumferential direction with spaces therebetween.
- Each of the second fixing portions 40 a is, for example, a through-hole. Each of the second fixing portions 40 a is disposed in an opposing position relative to each of the second attaching portions 24 b . In this state, a second fixing bolt 28 is inserted through each second fixing portion 40 a and each second attaching portion 24 b , and the second fixing bolt 28 is screwed to a nut member (not shown). With this, the second sprocket body 40 is fixed to the sprocket attaching arms 24 .
- the second annular portion 41 is provided to the outer perimeter of the second sprocket body 40 .
- the second annular portion 41 is made of metal, such as aluminum, titanium, or iron/stainless steel.
- a plurality of teeth 42 are formed on the outer perimeter of the second annular portion 41 .
- a plurality of teeth 42 includes a third tooth 42 a and a fourth tooth 42 b as described below.
- the teeth 42 are provided to the outer perimeter of the second annular portion 41 .
- the teeth 42 (for example, from a total number of 20 to 40) are disposed side-by-side in the circumferential direction on the outer perimeter of the second annular portion 41 .
- the teeth 42 are formed integrally with the outer perimeter portion of the second annular portion 41 .
- the teeth 42 are made of metal, such as aluminum, titanium, or, iron/stainless steel.
- the plurality of teeth 42 comprise a plurality of the third teeth 42 a (an example of the first tooth) and a plurality of the fourth teeth 42 b (an example of the second tooth).
- the third tooth 42 a and the fourth tooth 42 b are disposed alternately in the circumferential direction, that is, side-by-side in the circumferential direction.
- the third tooth 42 a is formed to be engageable with the outer link plates 2 a .
- the third tooth 42 a is formed to be engageable between the pairs of the outer link plates 2 a in the axial direction.
- the third tooth 42 a is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side.
- the third tooth 42 a preferably comprises a second recess 42 e (an example of a recess).
- the second recess 42 e is provided to a corner portion of the third tooth 42 a .
- the surface of the second recess 42 e that is located on the first side surface 14 a is flush with the surface of the fourth tooth 42 b on the first side surface 14 a .
- the surfaces of the second recesses 42 e that are located on the second side surface 14 b are flush with the surface of the fourth tooth 42 b on the second side surface 14 b.
- the second recesses 42 e are formed by press working, such as forging.
- press working such as forging.
- an example is shown of a case in which the second recesses 42 e are formed by press working, but the second recesses 42 e can also be formed by cutting.
- the second recesses 42 e are formed to face the end portion of the inner link plate 2 b , in the same way as the first recess 32 e described above to minimize interference between the third tooth 42 a and the inner link plates 2 b . In this way, excessive interference between the third tooth 42 a and the inner link plates 2 b can be avoided by the second recesses 42 e . Further, as shown in FIGS. 4 and 6 , by providing the second recesses 42 e to the third tooth 42 a , the third tooth 42 a is formed in a substantially + (plus sign) shape, seen from a radially outer side.
- the third tooth 42 a comprises a third maximum axial width W 3 (an example of a first axial chain engaging width).
- the third maximum axial width W 3 is the axial width of the portion where the dimension of the third tooth 42 a is the longest in the axial direction.
- the third maximum axial width W 3 is smaller than the first axial spacing L 1 .
- the third maximum axial width W 3 is larger than the second axial spacing L 2 in the pairs of the inner link plates 2 b.
- the fourth tooth 42 b is formed to be engageable with the inner link plates 2 b .
- the fourth tooth 42 b is formed to be engageable between the pairs of the inner link plates 2 b in the axial direction.
- the fourth tooth 42 b is formed in a substantially ⁇ (minus sign) shape, as seen from a radially outer side.
- the fourth tooth 42 b is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side.
- the fourth tooth 42 b comprises a fourth maximum axial width W 4 (an example of a second axial chain engaging width).
- the fourth maximum axial width W 4 is the axial width of the portion where the dimension of the fourth tooth 42 b is the longest in the axial direction.
- the fourth maximum axial width W 4 is smaller than the second axial spacing L 2 .
- the fourth maximum axial width W 4 is smaller than the third maximum axial width W 3 .
- the fourth tooth 42 b is formed by processing the fourth tooth 42 b in the following way, thereby obtaining the above configuration.
- the fourth tooth 42 b is formed by deformation of the base material of the teeth 42 .
- the fourth tooth 42 b is formed by press working. More specifically, the fourth tooth 42 b is formed by forging.
- the fourth maximum axial width W 4 of the fourth tooth 42 b is set by press working, for example, forging the fourth tooth 42 b in this way.
- the second shift regions 44 are provided for gear shifting the chain 2 .
- the second shift regions 44 are the regions in which the chain 2 engages with the teeth 42 of the first sprocket 14 during an upshifting operation from the second sprocket 16 to the first sprocket 14 , and the regions in which the chain 2 separates from the teeth 42 of the first sprocket 14 during a downshifting operation from the first sprocket 14 to the second sprocket 16 .
- Each of the second shift regions 44 comprises a plurality (for example, two) of second shifting teeth 42 c .
- the second shifting teeth 42 c are provided in the circumferential direction with spaces therebetween.
- Each of the second shifting teeth 42 c comprises a second guide surface 42 d .
- the second guide surfaces 42 d are provided on the fourth side surface 16 b (refer to FIG. 6 ), which is on the opposite side of the third side surface 16 a (refer to FIG. 1 ), and guides the chain 2 .
- the second guide surfaces 42 d are formed concavely, so that the thickness thereof gradually becomes thinner towards the side portion of the second shifting teeth 42 c.
- the third side surface 16 a of the second sprocket 16 is the front side surface of the crank assembly 10 when mounted on the bicycle.
- the third side surface 16 a is an outwardly facing side surface that faces axially outward away from the bicycle frame.
- the fourth side surface 16 b is the rear side surface of the crank assembly 10 when mounted on the bicycle.
- the fourth side surface 16 b is an inwardly facing side surface that faces axially inward towards the bicycle frame.
- the fourth side surface 16 b is located closer to the bicycle frame than is the third side surface 16 a when the crank assembly 10 is mounted on the bicycle.
- the second shift regions 44 do not comprise the protrusion or recess such as in the case of the first shift regions 34 .
- the second shift regions 44 can comprise at least either of a protrusion or a recess.
- the crank assembly 10 rotates in a forward rotation direction R when an upshifting operation is carried out from the second sprocket 16 to the first sprocket 14 by a front derailleur (not shown).
- a front derailleur (not shown).
- the chain 2 separates from the teeth of the second sprocket 16 .
- the chain 2 supported by one of the second protrusions 36 b , is moved to the radially outer side.
- the chain 2 supported by one of the first protrusions 36 a via one of the stepped portions 38 of one of the first shift regions 34 , is guided to and engages with the teeth 32 of the first sprocket 14 .
- the crank assembly 10 rotates in a forward rotation direction R when a downshifting operation is carried out from the first sprocket 14 to the second sprocket 16 by the front derailleur.
- the chain 2 separates from the teeth of the first sprocket 14 .
- the chain 2 is guided to the teeth 42 of the second sprocket 16 , and engages with the teeth 42 .
- the bicycle crank assembly 110 comprises the crank arm 12 , a first sprocket 114 (an example of a bicycle sprocket) and a second sprocket 116 (an example of a bicycle sprocket). Further, the first sprocket 114 and the second sprocket 116 are an example of a bicycle sprocket assembly.
- the configuration of the second embodiment is substantially the same as the first embodiment, except for the configurations of the first sprocket 114 and the second sprocket 116 . Accordingly, here, only the descriptions for the configurations of the first sprocket 114 and the second sprocket 116 are given, and the descriptions for the configurations that are substantially the same as the first embodiment are omitted. Meanwhile, configurations omitted here shall be in accordance with the configurations of the first embodiment. Further, configurations that are the same as the first embodiment are given the same reference symbols.
- the first sprocket 114 comprises the first sprocket body 30 (an example of a main body portion), the first annular portion 31 (an example of an annular portion), a plurality of teeth 132 (an example of a first tooth portion and a second tooth portion) and a pair of the first shift regions 34 (an example of a shift region).
- the configuration of the first sprocket body 30 , the configuration of the first annular portion 31 , and the configuration of the first shift region 34 are substantially the same as the configurations of the first embodiment, and thus the descriptions thereof are omitted. Further, regarding the configuration of the plurality of teeth 132 , only the configurations that are different from the configurations of the first embodiment will be described below.
- each of the plurality of first teeth 132 a (an example of the first tooth) included in the plurality of teeth 132 comprises a first main body portion 132 ab , the first recesses 32 e and a first additional portion 132 c .
- the first recesses 32 e are configured in the same way as in the first embodiment, and thus the description thereof is omitted.
- the first main body portion 132 ab is provided to the first annular portion 31 .
- the first main body portion 132 ab is integrally formed with the first annular portion 31 so as to protrude radially outward from the first annular portion 31 .
- the first main body portion 132 ab comprises a front surface 20 a and a back surface 20 b .
- the back surface 20 b is a surface on the opposite side of the front surface 20 a in the axial direction of the rotational center axis X.
- the first additional portion 132 c is attached to the first main body portion 132 ab to expand the width of the first main body portion 132 ab .
- the first additional portion 132 c is attached on each of the front surface 20 a and the back surface 20 b of the first main body portion 132 ab .
- a first maximum axial width W 1 is set to a prescribed width by attaching the first additional portion 132 c to each of the front surface 20 a and the back surface 20 b of the first main body portion 132 ab in this manner.
- the first additional portion 132 c is made of metal, such as aluminum, titanium, or iron/stainless steel. This first additional portion 132 c is attached to the first tooth 132 a by bonding, diffusion bonding, swaging or casting.
- the first additional portion 132 c is attached to each of the front surface 20 a and the back surface 20 b of the first main body portion 132 ab .
- the first maximum axial width W 1 can be set by attaching the first additional portion 132 c to only the front surface 20 a , or, only the back surface 20 b , of the first main body portion 132 ab.
- the second sprocket 116 comprises the second sprocket body 40 (an example of a main body portion), the second annular portion 41 (an example of an annular portion), a plurality of teeth 142 (an example of a first tooth portion and a second tooth portion), and a pair of second shift regions 44 (an example of a shift region).
- the configuration of the second sprocket body 40 , the configuration of the second annular portion 41 , and the configuration of the second shift region 44 are substantially the same as the configurations of the first embodiment, and thus the descriptions thereof are omitted. Further, regarding the configuration of the plurality of teeth 142 , only the configurations that are different from the configurations of the first embodiment will be described below.
- the teeth 142 include a plurality of third teeth 142 a .
- Each of the third teeth 142 a (examples of the first tooth) comprises a second main body portion 142 b , and a second additional portion 142 c .
- the configurations of the second main body portions 142 b and the second additional portions 142 c are substantially the same as the configurations of the above-described first main body portions 132 ab and the first additional portions 132 c . That is, the third maximum axial width W 3 is set to a prescribed width by attaching the second additional portions 142 c to each of the front surface 20 a and the back surface 20 b of the second main body portions 142 b.
- two front sprockets 14 and 16 were shown as an example of a bicycle sprocket assembly, but the present invention is not limited thereto.
- the present invention can be applied to a bicycle sprocket assembly provided with a single front sprocket that does not comprise a shift region.
- the second sprocket body 40 can be a separate body from the plurality of teeth 42 or 142 .
- the plurality of teeth 42 or 142 can be made of metal, while the second sprocket body 40 can be made of non-metal.
- weight reduction can be achieved by using aluminum, titanium, or iron/stainless steel for the metal, and synthetic resins such as carbon fiber-reinforced resin for the non-metal.
- the portion in which the first tooth 32 a or 132 a and the second tooth 32 b engage with the chain roller 2 c , and the portion in which the third tooth 42 a or 142 a and the fourth tooth 42 b engage with the chain roller 2 c , in the first and second embodiments, can be configured as shown in FIG. 8 .
- This configuration is substantially the same in the first sprocket 14 or 114 and the second sprocket 16 or 116 . Thus, here, the configuration will be described using the first tooth 232 a and the second tooth 232 b of the first sprockets 14 and 114 .
- the chain roller 2 c can be engaged between the first tooth 232 a and the second tooth 232 b (refer to FIGS. 1 and 5 ). As shown in FIG. 8 , each of the first tooth 232 a and the second tooth 232 b comprises a drive surface 233 and a non-drive surface 234 .
- Each of the first tooth 232 a and the second tooth 232 b comprises a front surface 20 a , a back surface (not shown), a drive surface 233 and a non-drive surface 234 .
- the back surface 20 b is a surface on the opposite side of the front surface 20 a in the axial direction of the rotational center axis X (the direction in FIG. 8 perpendicular to the paper surface).
- the drive surface 233 is a surface that couples the front surface 20 a and the back surface in the axial direction, to a downstream side in the forward rotation direction R.
- the drive surface 233 comprises a contact point CP and a first extension portion 233 a (an example of a drive surface extension portion).
- the contact point CP is where the chain roller 2 c comes into contact.
- the contact point CP is where the chain roller 2 c comes into contact with the drive surface 233 at the time of driving.
- the first extension portion 233 a is formed integrally with the drive surface 233 .
- the first extension portion 233 a extends in the circumferential direction radially outward from the contact point CP. Specifically, the first extension portion 233 a protrudes towards the downstream side in the forward rotation direction R, radially outward from the contact portion CP.
- the non-drive surface 234 is a surface that couples the front surface 20 a and the back surface in the axial direction, to an upstream side in the forward rotation direction R.
- the non-drive surface 234 is formed in line symmetry with the drive surface 233 with respect to a straight line CL that connects the rotational center axis X and the center position of the first tooth 232 a (second tooth 232 b ) in the circumferential direction.
- the non-drive surface 234 can be formed unsymmetrically relative to the drive surface 233 with respect to the straight line CL that connects the rotational center axis X and the center position of the first tooth 232 a (second tooth 232 b ) in the circumferential direction.
- the non-drive surface 234 comprises a second extension portion 234 a (an example of a non-drive surface extension portion).
- the radially outward movement of the chain roller 2 c is suppressed by the second extension portion 234 a .
- the second extension portion 234 a is formed integrally with the non-drive surface 234 .
- the non-drive surface 234 is formed in line symmetry with the drive surface 233 , the second extension portion 234 a extends to the opposite side of the first extension portion 233 a in the circumferential direction. That is, the second extension portion 234 a extends in a circumferential direction, for example, toward the upstream side in the forward rotation direction R.
- the drive force of the first sprocket 14 can by reliably transmitted to the chain roller 2 c , that is, the chain 2 , by the drive surface 233 . Further, the radially outward movement of the chain roller 2 c can be reliably suppressed by the drive surface 233 and the non-drive surface 234 .
- each of the first tooth 232 a and the second tooth 232 b comprises the drive surface 233 and the non-drive surface 234 .
- the configuration can be such that only the first tooth 232 a , or only the second tooth 232 b comprise a drive surface 233 and a non-drive surface 234 .
- the first tooth 232 a and/or the second tooth 232 b can be configured to comprise only a drive surface 233 , or only a non-drive surface 234 .
- An outline of the front sprockets 14 and 16 shown in the above first and second embodiments can be formed by a 3 D printer, after which the second tooth 32 b and the fourth tooth 42 b are formed by press working, such as forging.
- first tooth 32 a or 132 a and the third tooth 42 a or 142 a are formed in a substantially + shape
- the present invention is not limited thereto.
- at least a portion of the first tooth 32 a and the third tooth 42 a can be of another shape, such as a rhombic shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape.
- first tooth 332 a and/or third tooth 342 a are preferably of an octagonal shape, as seen from the radial direction of the bicycle sprocket to minimize interference between the first tooth 332 a and/or the third tooth 342 a and the inner link plates 2 b .
- excessive interference between the first tooth 332 a and/or the third tooth 342 a and the inner link plates 2 b can be avoided, and a tooth-shape for securely holding the outer link plates 2 a can be easily formed by press working, such as forging.
- an octagonal shape is not limited to a regular octagon shape, and may be any shape that has eight sides. Further, the eight sides that constitute the octagon are not limited to straight lines, and may be curved lines having a gentle curvature.
- the first tooth 332 a and the third tooth 342 a when the first tooth 332 a and the third tooth 342 a are of the octagonal shape described above, the first tooth 332 a and the third tooth 342 a comprise a first surface 352 a , a second surface 352 b , a third surface 352 c and an inclined portion 353 .
- the first surface 352 a is a surface of the first tooth 332 a on the first side surface 14 a side of the first sprocket 14 , and a surface of the third tooth 342 a on the third side surface 16 a of the second sprocket 16 .
- the second surface 352 b is a surface of the first teeth 332 a on the second side surface 14 b of the first sprocket 14 , and a surface of the third tooth 342 a on the fourth side surface 16 b of the second sprocket 16 .
- the third surface 352 c extends in the circumferential direction between the axial directions of the first surface 352 a and the second surface 352 b .
- the third surface 352 c comprises a drive surface 352 d , a non-drive surface 352 e and a distal end surface 352 f that couples the drive surface 352 d and the non-drive surface 352 e in the circumferential direction.
- the inclined portion 353 is configured to minimize (avoid excessive) interference with the inner link plates 2 b .
- the inclined portion 353 comprises a first chamfered surface 353 a , a second chamfered surface 353 b , a third chamfered surface 353 c and a fourth chamfered surface 353 d.
- the first chamfered surface 353 a is formed to extend from the first surface 352 a to the third surface 352 c on the drive side.
- the second chamfered surface 353 b is formed to extend from the second surface 352 b to the third surface 352 c on the drive side.
- the third chamfered surface 353 c is formed to extend from the first surface 352 a to the third surface 352 c on the non-drive side.
- the fourth chamfered surface 353 d is formed to extend from the second surface 352 b to the third surface 352 c on the non-drive side.
- the first chamfered surface 353 a is formed in a corner portion formed by the first surface 352 a and the third surface 352 c on the drive side.
- the second chamfered surface 353 b is formed in corner portions formed by the second surface 352 b and the third surface 352 c on the drive side.
- the third chamfered surface 353 c is formed in corner portions formed by the first surface 352 a and the third surface 352 c on the non-drive side.
- the fourth chamfered surface 353 d is formed in corner portions formed by the second surface 352 b and the third surface 352 c on the non-drive side.
- the first tooth 332 a and the third tooth 342 a on the drive side tend to more excessively interfere with the inner link plates 2 b . Therefore, the first chamfered surface 353 a and the second chamfered surface 353 b , which are formed on the drive side, preferably have a larger area compared to the third chamfered surface 353 c and the fourth chamfered surface 353 d , which are formed on the non-drive side.
- first through fourth chamfered surfaces 353 a , 353 b , 353 c and 353 d Excessive interference of the first tooth 332 a and the third tooth 342 a with the inner link plates 2 b can be avoided by the first through fourth chamfered surfaces 353 a , 353 b , 353 c and 353 d .
- the first through fourth chamfered surfaces 353 a , 353 b , 353 c and 353 d have a different shape from the recess in the above first and second embodiments, are inclined surfaces formed of straight or gently curved lines, and thus are easily formed by press working, such as forging.
- a first axial direction contact width L 3 of where the drive surface of the first tooth 332 a and the third tooth 342 a make contact with the chain roller 2 c is preferably formed to be of substantially the same length as a second axial direction contact width L 4 of where the drive surface of the second tooth 332 b and the fourth tooth 342 b make contact with the chain roller 2 c.
- first tooth 32 a or 132 a are formed in a substantially T-shape
- a portion of the first tooth 32 a can be of another shape, such as a rhombic shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape.
- each of the first shift regions 34 comprises one of the second protrusions 36 b , but the second protrusions 36 b do not have to be provided.
- the number of the plurality of sprocket attaching arms 24 is four, but the number of the sprocket attaching arms is not limited to four.
- the first sprocket 14 can comprise a ⁇ (minus sign) shaped second tooth 32 b in the first shift regions 34
- the second sprocket 16 can comprise a ⁇ (minus sign) shaped fourth tooth 42 b in the second shift regions 44 .
- the additional portion of the first tooth 32 a is made of metal, but the additional portion may be non-metallic.
- this additional portion is attached to the first tooth by bonding or integral molding. In this case, the noise caused during pedaling caused by contact between the chain and the sprocket teeth making can be reduced.
- At least one of the first tooth 32 a or 132 a or the second tooth 32 b or 132 b of the bicycle sprocket of the present invention can preferably comprise a plated layer.
- the plated layer is preferably a nickel plated layer, for the purpose of wear resistance.
- the plated layer is preferably a nickel chrome plated layer, for the purpose of rust resistance.
- the tooth teeth 32 a or 132 a and the second tooth 32 b or 132 b preferably comprise an electrodeposition coating layer, for the purpose of rust resistance and coloring.
- the first sprocket 14 can be configured from metal, and the first sprocket body 30 , the first annular portion 31 , and the first tooth portion 32 b can be integrally molded.
- the first sprocket body 30 , the first annular portion 31 , and the first tooth portion 32 b are formed of metal, such as aluminum, titanium, or iron/stainless steel.
- FIG. 11 An example of the first sprocket 314 configured in this way is shown in FIG. 11 .
- the configuration in FIG. 11 is substantially the same as the first and second embodiments described above, and the typical configurations are given the same reference symbols as the first embodiment.
- a first sprocket 214 can be configured as shown in FIGS. 12A and 12B . Meanwhile, in FIGS. 12A and 12B , configurations that are substantially the same as the first and second embodiments described above are given the same reference symbols as the first embodiment.
- a first through-hole 130 a is provided to the first sprocket body 30 .
- a second through-hole 130 b is provided to the first annular portion 31 .
- a ring member 130 c such as a washer, is disposed in the first through-hole 130 a .
- the first sprocket body 30 is integrally molded with the first annular portion 31 and the ring member 130 c , so that the inner perimeter surface of the ring member 130 c is substantially flush with the inner perimeter surface of the second through-hole 130 b.
- first fixing bolts 26 is inserted into each of the ring members 130 c , each of the second through-holes 130 b , and each of the first attaching portions 24 a , and is then screwed to a nut member (not shown). With this, the first sprocket body 30 is fixed to the sprocket attaching arms 24 .
- the second tooth 32 b are formed by a first pressing step (refer to part (B) of FIG. 13 ), a cutting step (refer to part (C) of FIG. 13 ) after the first pressing step, and a second pressing step (refer to part (D) of FIG. 13 ) after the cutting step.
- the second tooth 32 b comprise a fifth surface 52 a (an example of a first surface) and a sixth surface 52 b (an example of a first surface).
- the fifth surface 52 a is formed on the second tooth 32 a , on the first side surface 14 a (refer to FIG. 2 ) of the first sprocket 14 .
- the sixth surface 52 b is a surface that is located on the opposite side of the fifth surface 52 a in an axial direction parallel to the rotational center axis X.
- the sixth surface 52 b is formed on the second tooth 32 b , on the second side surface 14 b (refer to FIG. 4 ) of the first sprocket 14 .
- the surface on which the fifth surface 52 a of the second tooth 32 b is formed (first pressing portion 152 a described below) and the surface on which the sixth surface 52 b is formed (second pressing portion 152 c described below) are formed on substantially the same surface as the outer surface of the first annular portion 31 of the first sprocket 14 .
- a first pressing step is a process for pressing the fifth surface 52 a of the second tooth 32 b .
- the first pressing step with the first annular portion 31 in a fixed state, the fifth surface 52 a of the second tooth 32 b is pressed by a pressing member A of a pressing device (not shown).
- the first pressing portion 152 a where the pressing member A presses is the portion where the second tooth 32 b and the first recess 32 e are formed.
- the fifth surface 52 a of the second tooth portion 32 b is formed, and a portion on the sixth surface 52 b protrudes, which is located substantially on the opposite side of the first pressing portion 152 a .
- this portion will be referred to as the protrusion 152 b.
- the cutting step is a process for cutting the protrusion 152 b , which protrudes in the axial direction due to the first pressing step, on the sixth surface 52 b of the second tooth 32 b .
- the protrusion 152 b formed on the sixth surface 52 b is cut by a cutting device B.
- the protrusion 152 b is cut by the cutting device B so that the surface remaining after cutting is substantially the same surface as the outer surface of the first annular portion 31 .
- a second pressing step is a step for pressing the sixth surface 52 b side of the second tooth 32 b .
- the second pressing step in a state in which a mold D for forming the outer shape of the second tooth 32 b is abutting the first pressing portion 152 a , the sixth surface 52 b side of the second tooth 32 b is pressed by a pressing member C of the pressing device.
- the second pressing portion 152 c where the pressing member C presses is the portion where the tooth teeth 32 b and the first recess 32 e are formed.
- the sixth surface 52 b of the second tooth portion 32 b is formed.
- the teeth edge 52 c of the second tooth portion 32 b as well as the fifth surface 52 a and the sixth surface 52 b are formed.
- the second tooth 32 b can be formed by using the first pressing step, the cutting step and the second pressing step. Meanwhile, after the second tooth 32 b are formed in the above way, a polishing step for adjusting the shape of the second tooth 32 b , and a plating step (preferably, a nickel plating process) for improving the wear resistance of the second tooth 32 b can be added selectively.
- the second tooth 32 b are formed by press working and a cutting process, but the fourth tooth 42 b of the second sprocket 16 can be formed in the same way as well.
- front sprockets 14 and 16 were shown as examples of a bicycle sprocket, but the present invention is not limited thereto. The present invention can be applied to a rear sprocket as well.
- the present invention can be widely applied to bicycle sprockets and bicycle sprocket assemblies.
- the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps.
- the foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives.
- the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts unless otherwise stated.
- first and second may be used herein to describe various components these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, for example, a first component discussed above could be termed a second component and vice versa without departing from the teachings of the present invention.
- the term “attached” or “attaching”, as used herein, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to the intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e.
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Abstract
Description
- This application is a divisional application of U.S. patent application Ser. No. 15/218,677, which was filed on Jul. 25, 2016. This application claims priority to Japanese Patent Application No. 2015-200837, filed on Oct. 9, 2015, and Japanese Patent Application No. 2016-018340, filed on Feb. 2, 2016. The entire disclosures of Japanese Patent Application Nos. 2015-200837 and 2016-018340 and U.S. patent application Ser. No. 15/218,677 are hereby incorporated herein by reference.
- The present invention generally relates to a method of making a bicycle sprocket and a bicycle sprocket assembly.
- A conventional bicycle sprocket is provided to both a crank assembly and a rear wheel. A chain is engaged with the sprocket of the crank assembly and the sprocket of the rear wheel. Accordingly, the rotation of the crank assembly is transmitted to the rear wheel via the chain.
- In a chain, inner link plates and outer link plates are alternately coupled together to form a continuous loop. Further, the space between a pair of inner link plates facing each other is formed to be smaller than the space between a pair of outer link plates facing each other. Accordingly, if the sprocket teeth are formed so that the thickness (engaging width) of all of the sprocket teeth are the same, the gap between the outer link plates and the sprocket teeth will be larger than the gap between the inner link plates and the sprocket teeth, in the thickness direction of the sprocket.
- In this kind of conventional structure, the engagement between the chain and the sprocket tend to become loose, due to the gap between the outer link plates and the sprocket teeth in the thickness direction of the sprocket. Thus, a sprocket is proposed, which is formed so that the thickness of the teeth that engage the outer link plates is larger than the thickness of the teeth that engage the inner link plates (refer to U.S. Patent Application Publication No. 2013/0139642).
- Generally, the present disclosure is directed to various features of a bicycle sprocket. In one feature, a bicycle sprocket is provided with a first tooth and a second tooth in which the axial thickness or width of the first teeth is different from the axial thickness or width of the second tooth for increasing a chain holding force between the first and second teeth and the chain.
- In some conventional sprockets, the thickness of the teeth that engage the outer link plates is made larger than the thickness of the teeth that engage the inner link plates by cutting the teeth that engage the inner link plates (for example, refer to U.S. Patent Application Publication No. 2013/0139642, paragraph [0045]).
- In this case, there is a problem that the processing time to form a sprocket increases due to the additional time for cutting the teeth that engage the inner link plates. That is, when producing the above mentioned sprocket, it was difficult to improve the productivity of the sprocket.
- The present invention was developed in light of the above-described problem, and one object of the present invention is to provide a bicycle sprocket having high chain holding force and excellent productivity. Further, an object of the present invention is to provide a bicycle sprocket assembly having high chain holding force and excellent productivity.
- In view of the state of the known technology and in accordance with a first aspect of the present disclosure, a method of making a bicycle sprocket having a rotational center axis is provided. The method comprising providing an annular portion and forming a first tooth and a second tooth. The annular portion is made of a base material and has a plurality of teeth integrally formed on an outer perimeter of the annular portion. At least one of the plurality of teeth is processed to form the first tooth, and at least one other of the plurality of teeth is processed to form the second tooth. The first tooth is formed to have a first axial chain engaging width that is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link coupled to the outer link. The second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing. The second tooth being formed by deforming the base material.
- In the bicycle sprocket made according to the present method, the first axial chain engaging width of the first tooth is smaller than the first axial spacing in the outer link, and larger than the second axial spacing in the inner link. Further, the second axial chain engaging width of the second tooth is smaller than the second axial spacing. Accordingly, the chain can be held securely by the sprocket. Further, since the second tooth is formed by deformation of the material, the productivity of the sprocket can be improved compared to that of the prior art.
- In accordance with a second aspect of the present invention, the method of making a bicycle sprocket includes forming a recess in the first tooth, the recess being configured to minimize interference with the inner link. In this way, even if the first tooth is disposed between the outer link, excessive interference with the inner link can be avoided by the recess.
- In accordance with a third aspect of the present invention, the method of making a bicycle sprocket includes forming the recess and the second tooth together by the press working. Since the recess and the second tooth are formed together by press working, the productivity of bicycle sprocket can be improved.
- In accordance with a fourth aspect of the present invention, the method of making a bicycle sprocket includes forming four of the recesses in the first tooth such that the first tooth has a plus-sign shape when viewed from a radially outer side. Thus, the first tooth can be even more reliably prevented from interfering with the inner link of the bicycle chain.
- In accordance with a fifth aspect of the present invention, the method of making a bicycle sprocket includes forming the four recesses and the second tooth together by the press working. In this way, by forming the four recesses and the second tooth together by press working, the first tooth can be even more reliably prevented from interfering with the inner link of the bicycle chain while also improving the productivity of the bicycle sprocket.
- In accordance with a sixth aspect of the present invention, the method of making a bicycle sprocket includes forming the second tooth using a first press working step, a cutting step performed after the first press working step, and a second press working step performed after the cutting step. In this way, the second tooth can be formed reliably and accurately.
- In accordance with a seventh aspect of the present invention, the first press working step includes pressing one axial side of the second tooth and forming a protrusion on an opposite axial side of the second tooth, the cutting step includes cutting the protrusion, and the second press working step includes pressing the opposite axial side of the second tooth to achieve the second axial chain engaging width.
- In accordance with an eighth aspect of the present invention, a method of making a bicycle sprocket having a rotational center axis is provided. The method comprises providing an annular portion and forming a first tooth and a second tooth. The annular portion is made of a base material having a plurality of teeth integrally formed on an outer perimeter of the annular portion. At least one of the plurality of teeth is processed to form the first tooth, and at least one other of the plurality of teeth is processed to form the second tooth. The first tooth is formed to have a maximum axial width smaller than a first axial chain engaging width, which is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link coupled to the outer link. Four recesses are formed in the first tooth such that the first tooth has a plus-sign shape when viewed from a radially outer side. A first additional portion is attached to the first tooth to expand the maximum axial width of the first tooth to the first axial chain engaging width. The second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing. The second tooth is formed by deforming the base material.
- With the eight aspect of the present invention, the first axial chain engaging width of the first tooth is smaller than the first axial spacing in the outer link, and larger than the second axial spacing in the inner link. Further, the second axial chain engaging width of the second tooth is smaller than the second axial spacing. Accordingly, the chain can be held securely by the sprocket. Further, since the second tooth is formed by deformation of the material, the productivity of the sprocket can be improved compared to that of the prior art. Also, with the eight aspect, the material of the additional portion can be chosen freely by attaching the additional portion to the main body portion.
- In accordance with a ninth aspect of the present invention, the method of making a bicycle sprocket includes forming the four recesses in the fourth tooth and forming the second tooth together by the press working. Since the recess and the second tooth are formed together by press working, the productivity of bicycle sprocket can be improved.
- According to the present invention, a bicycle sprocket having high chain holding force and excellent productivity can be provided. Further, a bicycle sprocket assembly having high chain holding force and excellent productivity can be provided.
- Referring now to the attached drawings which form a part of this original disclosure.
-
FIG. 1 is a front side elevational view of a bicycle crank assembly in accordance with first and second embodiments. -
FIG. 2 is a front side oblique view of the first sprocket of the bicycle crank assembly illustrated inFIG. 1 according to the first embodiment. -
FIG. 3 is a rear side elevational view of the first sprocket according to the first embodiment. -
FIG. 4 is a partial rear side oblique view of the first and second sprockets according to the first embodiment. -
FIG. 5 is a partial edge view of the first sprocket and the second sprocket according to the first embodiment, as seen from a radially outer side direction. -
FIG. 6 is a front side oblique view of the second sprocket according to the first embodiment. -
FIG. 7 is a cross-sectional view corresponding to the first tooth of the first sprocket and the third tooth of the second sprocket according to the second embodiment. -
FIG. 8 is a front side view corresponding to the first tooth of the first sprocket and the third tooth of the second sprocket according to another embodiment of the present invention. -
FIG. 9 is a partial front side view of the teeth portion of the first and second sprockets according to another embodiment. -
FIG. 10 is a partial edge view of the teeth portion of the first and second sprockets according to another embodiment, as seen from a radially outer side direction. -
FIG. 11 is a front side elevational view of the first sprocket according to another embodiment. -
FIG. 12A is a front side elevational view of the first sprocket according to another embodiment. -
FIG. 12B is a partial cross-sectional view of the first sprocket illustrated inFIG. 12A . -
FIG. 13 is a schematic diagram illustrating a forming state of the second tooth and the fourth tooth according to another embodiment. - Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the bicycle field from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
- As shown in
FIG. 1 , a bicycle crank assembly 10 (hereinafter referred to as crank assembly) is illustrated in accordance with a first embodiment. The bicycle crankassembly 10 basically comprises acrank arm 12, a first sprocket 14 (an example of a bicycle sprocket), and a second sprocket 16 (an example of a bicycle sprocket). Further, thefirst sprocket 14 and thesecond sprocket 16 are examples of a bicycle sprocket assembly. - In the
crank assembly 10, thefirst sprocket 14 and thesecond sprocket 16 are front sprockets that are configured to engage with abicycle chain 2. Thesecond sprocket 16 has fewer teeth than thefirst sprocket 14. Thebicycle chain 2 comprises a plurality of pairs ofouter link plates 2 a, a plurality of pairs ofinner link plates 2 b and a plurality ofchain rollers 2 c. Thechain rollers 2 c couple adjacent pairs of theouter link plates 2 a and theinner link plates 2 b. - The
crank arm 12 is integrally and non-rotatably coupled to acrankshaft 19. Thecrank arm 12 comprises asprocket attaching portion 20 and anarm portion 22. Thearm portion 22 is non-rotatably with respect to thesprocket attaching portion 20. Thearm portion 22 is provided integrally with thesprocket attaching portion 20 as a non-separable member, or separately detachable from thesprocket attaching portion 20. - The
sprocket attaching portion 20 comprises a plurality (for example, four) ofsprocket attaching arms 24. Thesprocket attaching arms 24 are disposed in the circumferential direction with spaces therebetween. The intervals of thesprocket attaching arms 24 in the circumferential direction are regular intervals. Here, an example is shown of a case in which the intervals of thesprocket attaching arms 24 in the circumferential direction are regular intervals, but the intervals of thesprocket attaching arms 24 in the circumferential direction can be irregular intervals. - Each of the
sprocket attaching arms 24 comprises a first attachingportion 24 a and a second attachingportion 24 b. The first attachingportions 24 a are configured for attaching thefirst sprocket 14. The first attachingportions 24 a are formed on distal end portions of thesprocket attaching arms 24. Each of the first attachingportions 24 a is, for example, a through-hole. Thefirst sprocket 14 is fixed to the first attachingportions 24 a. - The second attaching
portions 24 b are configured for attaching thesecond sprocket 16. The second attachingportions 24 b are formed on proximal end portions of thesprocket attaching arms 24, radially inward from the first attachingportions 24 a. The second attachingportions 24 b are, for example, blind screw holes. Thesecond sprocket 16 is fixed to the second attachingportions 24 b. - The
arm portion 22 is provided integrally with or separately from thesprocket attaching portion 20. Here, thearm portion 22 is formed integrally with thesprocket attaching portion 20. Apedal attaching portion 22 a is provided on the distal end portion of thearm portion 22. A pedal (not shown) can be mounted to thepedal attaching portion 22 a. Acoupling hole 22 b is provided to the proximal end portion of thearm portion 22. Thecrankshaft 19 is integrally and non-rotatably coupled to thecoupling hole 22 b. - As shown in
FIGS. 2 to 5 , thefirst sprocket 14 comprises a rotational center axis X. Thefirst sprocket 14 comprises a first sprocket body 30 (an example of a main body portion), a first annular portion 31 (an example of an annular portion), a plurality of teeth 32 (an example of a first tooth portion and a second tooth portion), and a pair of first shift regions 34 (refer toFIGS. 3 and 4 ; an example of a shift region). - The
first sprocket body 30 is non-metallic, and made of synthetic resin such as carbon fiber-reinforced resin. Thefirst sprocket body 30 is formed integrally with the firstannular portion 31. As shown inFIGS. 2 to 4 , thefirst sprocket body 30 comprises a plurality (for example, four) of first fixingportions 30 a. The plurality of first fixingportions 30 a are disposed in the circumferential direction with spaces therebetween. - Each of the
first fixing portions 30 a is, for example, a through-hole. Each of thefirst fixing portions 30 a is disposed in an opposing position relative to each of the first attachingportions 24 a. In this state, a first fixing bolt 26 (refer toFIG. 1 ) is inserted through each of the first fixingportion 30 a and each of the first attachingportion 24 a, and is screwed to a nut member (not shown). With this, thefirst sprocket body 30 is non-movably fixed to thesprocket attaching arms 24. - The first
annular portion 31 is attached to thefirst sprocket body 30. Specifically, the firstannular portion 31 is attached to the outer perimeter of thefirst sprocket body 30. The firstannular portion 31 is made of metal, such as aluminum, titanium, or iron/stainless steel. A plurality ofteeth 32 are formed on the outer perimeter of the firstannular portion 31. - The plurality of
teeth 32 include afirst tooth 32 a and asecond tooth 32 b as described below. The plurality ofteeth 32 are provided to the outer perimeter of the firstannular portion 31. Specifically, the plurality of teeth 32 (for example, from a total number of 30 to 60) are disposed side-by-side in the circumferential direction on the outer perimeter of the firstannular portion 31. Theteeth 32 are formed integrally with the outer perimeter portion of the firstannular portion 31. The plurality ofteeth 32 are made of metal, such as aluminum, titanium, or, iron/stainless steel. - As mentioned above, the plurality of
teeth 32 comprise a plurality of thefirst teeth 32 a (an example of a first tooth) and a plurality of thesecond teeth 32 b (an example of a second tooth). Thefirst tooth 32 a and thesecond tooth 32 b are disposed alternately in the circumferential direction, that is, side-by-side in the circumferential direction. - The
first tooth 32 a is formed to be engageable with theouter link plates 2 a. Specifically, thefirst tooth 32 a is formed to be engageable between the pairs of theouter link plates 2 a in the axial direction. Thefirst tooth 32 a is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side. The axial direction includes the direction in which the rotational center axis X extends, and the directions that are parallel to the rotational center axis X. The axial direction used here corresponds to the directions that are parallel to the rotational center axis X. - As shown in
FIG. 4 , thefirst tooth 32 a preferably comprises afirst recess 32 e (an example of a recess). The first recesses 32 e are provided to each corner portion of thefirst tooth 32 a. The surfaces of thefirst recesses 32 e that are located on thefirst side surface 14 a are preferably flush with the surfaces of thesecond tooth 32 b on thefirst side surface 14 a. Similarly, the surfaces of thefirst recesses 32 e on thesecond side surface 14 b are preferably flush with the surfaces of thesecond tooth 32 b on thesecond side surface 14 b. - Here, the
first side surface 14 a (refer toFIG. 1 ) is the front side surface of thecrank assembly 10 when mounted on the bicycle. In other words, thefirst side surface 14 a is an outwardly facing side surface that faces axially outward away from the bicycle frame. Further, thesecond side surface 14 b (refer toFIGS. 3 and 4 ) is the rear side surface of thecrank assembly 10 when mounted on the bicycle. In other words, thesecond side surface 14 b is an inwardly facing side surface that faces axially inward towards the bicycle frame. Thus, thesecond side surface 14 b is located closer to the bicycle frame than is thefirst side surface 14 a when thecrank assembly 10 is mounted on the bicycle. - The first recesses 32 e are formed by press working, such as forging. Here, an example is shown of a case in which the
first recesses 32 e are formed by press working. However, thefirst recesses 32 e can also be formed by cutting. - As shown in
FIG. 5 , thefirst recesses 32 e are formed to face the end portion of theinner link plate 2 b to minimize interference between thefirst teeth 32 a and theinner link plates 2 b. In this way, excessive interference between thefirst tooth 32 a and theinner link plates 2 b can be avoided by thefirst recesses 32 e. Further, as shown inFIGS. 2, 4 and 5 , by providing thefirst recesses 32 e to thefirst tooth 32 a, thefirst tooth 32 a (excluding thefirst tooth 32 a 1 and thefirst tooth 32 a 2 which are for gear shifting) are formed in a substantially + (plus sign) shape, seen from a radially outer side. - Here, as shown in
FIGS. 2 to 3 , the plurality offirst teeth 32 a comprises a plurality (for example, two) offirst teeth 32 a 1 configured for gear shifting, and a plurality (for example, two) offirst teeth 32 a 2 configured for gear shifting. Thefirst tooth 32 a 1 is configured for downshifting in which thechain 2 moves from thefirst sprocket 14 to thesecond sprocket 16. Thefirst tooth 32 a 2 is configured for upshifting in which thechain 2 moves from thesecond sprocket 16 to thefirst sprocket 14. Thefirst tooth 32 a 1 and thefirst tooth 32 a 2 are preferably formed in a substantially T-shape, when seen from a radially outer side, by being provided with thefirst recesses 32 e as described above. - As shown in
FIG. 5 , thefirst teeth 32 a comprise a first maximum axial width W1 (an example of a first axial chain engaging width). The first maximum axial width W1 is the axial width in of the portion where the dimension of thefirst tooth 32 a is the longest in the axial direction. The first maximum axial width W1 is smaller than a first axial spacing L1 in the pairs of theouter link plates 2 a. Further, the first maximum axial width W1 is larger than a second axial spacing L2 in the pairs of theinner link plates 2 b. - The first axial spacing L1 is the space in the axial direction between the surfaces that face each other of a pair of the
outer link plates 2 a. The second axial spacing L2 is the space in the axial direction between the surfaces that face each other of a pair of theinner link plates 2 b. - As shown in
FIGS. 2 to 4 , thesecond tooth 32 b is formed to be engageable with theinner link plates 2 b. Specifically, thesecond tooth 32 b is formed to be engageable between the pairs of theinner link plates 2 b in the axial direction. - The
second tooth 32 b is preferably formed in a substantially − (minus sign) shape, as seen from a radially outer side. Thesecond tooth 32 b is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side. - As shown in
FIG. 5 , thesecond tooth 32 b comprises a second maximum axial width W2 (an example of a second axial chain engaging width). The second maximum axial width W2 is the axial width of the portion where the dimension of thesecond tooth 32 b is the longest in the axial direction. The second maximum axial width W2 is smaller than the second axial spacing L2 described above. The second maximum axial width W2 is smaller than the first maximum axial width W1. - The
second tooth 32 b is formed by processing thesecond tooth 32 b in the following way, thereby obtaining the above configuration. Thesecond tooth 32 b is formed by deformation of the base material of theteeth 32. Specifically, thesecond tooth 32 b is formed by press working. More specifically, thesecond tooth 32 b is formed by forging. Specifically, thesecond tooth 32 b is formed together with thefirst recesses 32 e by forging. The second maximum axial width W2 of thesecond tooth 32 b is set by press working, for example, forging thesecond tooth 32 b in this way. - The
first shift regions 34 are provided for gear shifting thechain 2. Thefirst shift regions 34 are the regions in which thechain 2 engages with theteeth 32 of thefirst sprocket 14 during an upshifting operation from thesecond sprocket 16 to thefirst sprocket 14. Further, thefirst shift regions 34 are the regions in which the chain engages with theteeth 32 of thefirst sprocket 14 during a downshifting operation from thefirst sprocket 14 to thesecond sprocket 16. - As shown in
FIGS. 2 to 4 , each of thefirst shift regions 34 comprises a plurality of the first shiftingteeth 32 c. Here, the plurality (for example, two) of thefirst teeth 32 a 1 for gear shifting correspond to the first shiftingteeth 32 c. Further, the two of thesecond teeth 32 b adjacent to each of the first shiftingteeth 32 a 1 for gear shifting correspond to the first shiftingteeth 32 c. - As shown in
FIGS. 2 and 3 , the first shiftingteeth 32 c comprise afirst guide surface 32 d. Thefirst guide surface 32 d is a surface for guiding thechain 2. Thefirst guide surface 32 d is provided to the first shiftingteeth 32 c, on the side of thefirst surface 14 a (refer toFIG. 2 ) or on the side of thesecond surface 14 b (refer toFIGS. 3 and 4 ) of thefirst sprocket 14. Thefirst guide surface 32 d is formed concavely, so that the thickness thereof gradually becomes thinner towards the side portion of the first shiftingteeth 32 c. - Further, each of the
first shift regions 34 preferably comprises afirst protrusion 36 a and asecond protrusion 36 b. Thefirst protrusions 36 a and thesecond protrusions 36 b are provided to thefirst sprocket body 30, and are configured to support thechain 2 during shifting operation. Here, a first pair of the first andsecond protrusions second protrusions first sprocket 14. - The
first protrusions 36 a are protrudingly provided on thesecond side surface 14 b of thefirst sprocket body 30, for guiding thechain 2 to theteeth 32 of thefirst sprocket 14. For example, thefirst protrusions 36 a guide thechain 2 to thesecond tooth 32 b shown by the hatching inFIG. 3 . Thesecond protrusions 36 b are protrudingly provided on thesecond side surface 14 b of thefirst sprocket body 30, for guiding thechain 2 to thefirst protrusions 36 a. - Further, as shown in
FIGS. 3 and 4 , each of thefirst shift regions 34 comprises a steppedportion 38. The steppedportions 38 are for facilitating the engagement of thechain 2, which is supported by one of thefirst protrusions 36 a, with theteeth 32 of thefirst sprocket 14. The steppedportions 38 are provided on thefirst side surface 14 a, radially inward from the tooth-bottoms of the plurality ofteeth 32. Further, the steppedportions 38 are provided to the downstream side in the forward rotation direction R from thefirst protrusion 36 a. The steppedportions 38 are concavely formed in a substantially triangular shape. - As shown in
FIGS. 4 and 6 , thesecond sprocket 16 comprises a rotational center axis Y. The rotational center axis Y and the rotational center axis X are concentric. Thesecond sprocket 16 comprises a second sprocket body 40 (an example of a main body portion), a second annular portion 41 (an example of an annular portion), a plurality of teeth 42 (an example of a first tooth portion and a second tooth portion), and a pair of second shift regions 44 (an example of a shift region). - The
second sprocket body 40 is made of metal, such as aluminum, titanium, or iron/stainless steel. Thesecond sprocket body 40 comprises a plurality (for example, four) ofsecond fixing portions 40 a. Thesecond fixing portions 40 a are disposed in the circumferential direction with spaces therebetween. - Each of the
second fixing portions 40 a is, for example, a through-hole. Each of thesecond fixing portions 40 a is disposed in an opposing position relative to each of the second attachingportions 24 b. In this state, asecond fixing bolt 28 is inserted through each second fixingportion 40 a and each second attachingportion 24 b, and thesecond fixing bolt 28 is screwed to a nut member (not shown). With this, thesecond sprocket body 40 is fixed to thesprocket attaching arms 24. - The second
annular portion 41 is provided to the outer perimeter of thesecond sprocket body 40. The secondannular portion 41 is made of metal, such as aluminum, titanium, or iron/stainless steel. A plurality ofteeth 42 are formed on the outer perimeter of the secondannular portion 41. - A plurality of
teeth 42 includes athird tooth 42 a and afourth tooth 42 b as described below. Theteeth 42 are provided to the outer perimeter of the secondannular portion 41. Specifically, the teeth 42 (for example, from a total number of 20 to 40) are disposed side-by-side in the circumferential direction on the outer perimeter of the secondannular portion 41. Theteeth 42 are formed integrally with the outer perimeter portion of the secondannular portion 41. Theteeth 42 are made of metal, such as aluminum, titanium, or, iron/stainless steel. - As mentioned above, the plurality of
teeth 42 comprise a plurality of thethird teeth 42 a (an example of the first tooth) and a plurality of thefourth teeth 42 b (an example of the second tooth). Thethird tooth 42 a and thefourth tooth 42 b are disposed alternately in the circumferential direction, that is, side-by-side in the circumferential direction. - The
third tooth 42 a is formed to be engageable with theouter link plates 2 a. Specifically, thethird tooth 42 a is formed to be engageable between the pairs of theouter link plates 2 a in the axial direction. Thethird tooth 42 a is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side. - As shown in
FIG. 6 , thethird tooth 42 a preferably comprises asecond recess 42 e (an example of a recess). Thesecond recess 42 e is provided to a corner portion of thethird tooth 42 a. The surface of thesecond recess 42 e that is located on thefirst side surface 14 a is flush with the surface of thefourth tooth 42 b on thefirst side surface 14 a. The surfaces of thesecond recesses 42 e that are located on thesecond side surface 14 b are flush with the surface of thefourth tooth 42 b on thesecond side surface 14 b. - The second recesses 42 e are formed by press working, such as forging. Here, an example is shown of a case in which the
second recesses 42 e are formed by press working, but thesecond recesses 42 e can also be formed by cutting. - The second recesses 42 e are formed to face the end portion of the
inner link plate 2 b, in the same way as thefirst recess 32 e described above to minimize interference between thethird tooth 42 a and theinner link plates 2 b. In this way, excessive interference between thethird tooth 42 a and theinner link plates 2 b can be avoided by thesecond recesses 42 e. Further, as shown inFIGS. 4 and 6 , by providing thesecond recesses 42 e to thethird tooth 42 a, thethird tooth 42 a is formed in a substantially + (plus sign) shape, seen from a radially outer side. - As shown in
FIG. 5 , thethird tooth 42 a comprises a third maximum axial width W3 (an example of a first axial chain engaging width). The third maximum axial width W3 is the axial width of the portion where the dimension of thethird tooth 42 a is the longest in the axial direction. The third maximum axial width W3 is smaller than the first axial spacing L1. Further, the third maximum axial width W3 is larger than the second axial spacing L2 in the pairs of theinner link plates 2 b. - As shown in
FIGS. 4 to 6 , thefourth tooth 42 b is formed to be engageable with theinner link plates 2 b. Specifically, thefourth tooth 42 b is formed to be engageable between the pairs of theinner link plates 2 b in the axial direction. - The
fourth tooth 42 b is formed in a substantially − (minus sign) shape, as seen from a radially outer side. Thefourth tooth 42 b is formed in a divergently tapered shape so that the width in the axial direction gradually becomes smaller toward the radially outer side. - As shown in
FIG. 5 , thefourth tooth 42 b comprises a fourth maximum axial width W4 (an example of a second axial chain engaging width). The fourth maximum axial width W4 is the axial width of the portion where the dimension of thefourth tooth 42 b is the longest in the axial direction. The fourth maximum axial width W4 is smaller than the second axial spacing L2. Further, the fourth maximum axial width W4 is smaller than the third maximum axial width W3. - The
fourth tooth 42 b is formed by processing thefourth tooth 42 b in the following way, thereby obtaining the above configuration. Thefourth tooth 42 b is formed by deformation of the base material of theteeth 42. Specifically, thefourth tooth 42 b is formed by press working. More specifically, thefourth tooth 42 b is formed by forging. The fourth maximum axial width W4 of thefourth tooth 42 b is set by press working, for example, forging thefourth tooth 42 b in this way. - The
second shift regions 44 are provided for gear shifting thechain 2. Thesecond shift regions 44 are the regions in which thechain 2 engages with theteeth 42 of thefirst sprocket 14 during an upshifting operation from thesecond sprocket 16 to thefirst sprocket 14, and the regions in which thechain 2 separates from theteeth 42 of thefirst sprocket 14 during a downshifting operation from thefirst sprocket 14 to thesecond sprocket 16. - Each of the
second shift regions 44 comprises a plurality (for example, two) of second shiftingteeth 42 c. Thesecond shifting teeth 42 c are provided in the circumferential direction with spaces therebetween. Each of the second shiftingteeth 42 c comprises asecond guide surface 42 d. The second guide surfaces 42 d are provided on thefourth side surface 16 b (refer toFIG. 6 ), which is on the opposite side of thethird side surface 16 a (refer toFIG. 1 ), and guides thechain 2. The second guide surfaces 42 d are formed concavely, so that the thickness thereof gradually becomes thinner towards the side portion of the second shiftingteeth 42 c. - Here, the
third side surface 16 a of thesecond sprocket 16 is the front side surface of thecrank assembly 10 when mounted on the bicycle. In other words, thethird side surface 16 a is an outwardly facing side surface that faces axially outward away from the bicycle frame. Thefourth side surface 16 b is the rear side surface of thecrank assembly 10 when mounted on the bicycle. In other words, thefourth side surface 16 b is an inwardly facing side surface that faces axially inward towards the bicycle frame. Thus, thefourth side surface 16 b is located closer to the bicycle frame than is thethird side surface 16 a when thecrank assembly 10 is mounted on the bicycle. - Here, an example is shown of a case in which the
second shift regions 44 do not comprise the protrusion or recess such as in the case of thefirst shift regions 34. However, thesecond shift regions 44 can comprise at least either of a protrusion or a recess. - In the
crank assembly 10 configured in the way described above, thecrank assembly 10 rotates in a forward rotation direction R when an upshifting operation is carried out from thesecond sprocket 16 to thefirst sprocket 14 by a front derailleur (not shown). In this state, when the front derailleur moves from a position opposed to thesecond sprocket 16 to a position opposed to thefirst sprocket 14, thechain 2 separates from the teeth of thesecond sprocket 16. Then, thechain 2, supported by one of thesecond protrusions 36 b, is moved to the radially outer side. Then, thechain 2, supported by one of thefirst protrusions 36 a via one of the steppedportions 38 of one of thefirst shift regions 34, is guided to and engages with theteeth 32 of thefirst sprocket 14. - On the other hand, the
crank assembly 10 rotates in a forward rotation direction R when a downshifting operation is carried out from thefirst sprocket 14 to thesecond sprocket 16 by the front derailleur. In this state, when the front derailleur moves from a position opposed to thefirst sprocket 14 to a position opposed to thesecond sprocket 16, thechain 2 separates from the teeth of thefirst sprocket 14. Then, thechain 2 is guided to theteeth 42 of thesecond sprocket 16, and engages with theteeth 42. - As shown in
FIG. 1 , a bicycle crank assembly 110 according to the second embodiment is illustrated. The bicycle crankassembly 110 comprises thecrank arm 12, a first sprocket 114 (an example of a bicycle sprocket) and a second sprocket 116 (an example of a bicycle sprocket). Further, thefirst sprocket 114 and thesecond sprocket 116 are an example of a bicycle sprocket assembly. - The configuration of the second embodiment is substantially the same as the first embodiment, except for the configurations of the
first sprocket 114 and thesecond sprocket 116. Accordingly, here, only the descriptions for the configurations of thefirst sprocket 114 and thesecond sprocket 116 are given, and the descriptions for the configurations that are substantially the same as the first embodiment are omitted. Meanwhile, configurations omitted here shall be in accordance with the configurations of the first embodiment. Further, configurations that are the same as the first embodiment are given the same reference symbols. - The
first sprocket 114 comprises the first sprocket body 30 (an example of a main body portion), the first annular portion 31 (an example of an annular portion), a plurality of teeth 132 (an example of a first tooth portion and a second tooth portion) and a pair of the first shift regions 34 (an example of a shift region). - Here, the configuration of the
first sprocket body 30, the configuration of the firstannular portion 31, and the configuration of thefirst shift region 34 are substantially the same as the configurations of the first embodiment, and thus the descriptions thereof are omitted. Further, regarding the configuration of the plurality ofteeth 132, only the configurations that are different from the configurations of the first embodiment will be described below. - As shown in
FIG. 7 , each of the plurality offirst teeth 132 a (an example of the first tooth) included in the plurality ofteeth 132 comprises a firstmain body portion 132 ab, thefirst recesses 32 e and a firstadditional portion 132 c. The first recesses 32 e are configured in the same way as in the first embodiment, and thus the description thereof is omitted. - The first
main body portion 132 ab is provided to the firstannular portion 31. Specifically, the firstmain body portion 132 ab is integrally formed with the firstannular portion 31 so as to protrude radially outward from the firstannular portion 31. The firstmain body portion 132 ab comprises afront surface 20 a and aback surface 20 b. Theback surface 20 b is a surface on the opposite side of thefront surface 20 a in the axial direction of the rotational center axis X. - The first
additional portion 132 c is attached to the firstmain body portion 132 ab to expand the width of the firstmain body portion 132 ab. Specifically, the firstadditional portion 132 c is attached on each of thefront surface 20 a and theback surface 20 b of the firstmain body portion 132 ab. A first maximum axial width W1 is set to a prescribed width by attaching the firstadditional portion 132 c to each of thefront surface 20 a and theback surface 20 b of the firstmain body portion 132 ab in this manner. The firstadditional portion 132 c is made of metal, such as aluminum, titanium, or iron/stainless steel. This firstadditional portion 132 c is attached to thefirst tooth 132 a by bonding, diffusion bonding, swaging or casting. - Here, an example is shown in which the first
additional portion 132 c is attached to each of thefront surface 20 a and theback surface 20 b of the firstmain body portion 132 ab. Instead of this, the first maximum axial width W1 can be set by attaching the firstadditional portion 132 c to only thefront surface 20 a, or, only theback surface 20 b, of the firstmain body portion 132 ab. - The
second sprocket 116 comprises the second sprocket body 40 (an example of a main body portion), the second annular portion 41 (an example of an annular portion), a plurality of teeth 142 (an example of a first tooth portion and a second tooth portion), and a pair of second shift regions 44 (an example of a shift region). - Here, the configuration of the
second sprocket body 40, the configuration of the secondannular portion 41, and the configuration of thesecond shift region 44 are substantially the same as the configurations of the first embodiment, and thus the descriptions thereof are omitted. Further, regarding the configuration of the plurality ofteeth 142, only the configurations that are different from the configurations of the first embodiment will be described below. - Further, the
teeth 142 include a plurality of third teeth 142 a. Each of the third teeth 142 a (examples of the first tooth) comprises a secondmain body portion 142 b, and a secondadditional portion 142 c. The configurations of the secondmain body portions 142 b and the secondadditional portions 142 c are substantially the same as the configurations of the above-described firstmain body portions 132 ab and the firstadditional portions 132 c. That is, the third maximum axial width W3 is set to a prescribed width by attaching the secondadditional portions 142 c to each of thefront surface 20 a and theback surface 20 b of the secondmain body portions 142 b. - One embodiment of the present invention was described above, however the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. In particular, the various embodiments and modified examples described in the present Specification can be freely combined according to necessity.
- In the first and second embodiments, two
front sprockets 14 and 16 (114, 116) were shown as an example of a bicycle sprocket assembly, but the present invention is not limited thereto. The present invention can be applied to a bicycle sprocket assembly provided with a single front sprocket that does not comprise a shift region. - (b) In the first and second embodiments, a case in which the
second sprocket body 40 and the plurality ofteeth second sprocket body 40 can be a separate body from the plurality ofteeth teeth second sprocket body 40 can be made of non-metal. In this case, weight reduction can be achieved by using aluminum, titanium, or iron/stainless steel for the metal, and synthetic resins such as carbon fiber-reinforced resin for the non-metal. - (c) The portion in which the
first tooth second tooth 32 b engage with thechain roller 2 c, and the portion in which thethird tooth 42 a or 142 a and thefourth tooth 42 b engage with thechain roller 2 c, in the first and second embodiments, can be configured as shown inFIG. 8 . - This configuration is substantially the same in the
first sprocket second sprocket first tooth 232 a and thesecond tooth 232 b of thefirst sprockets - The
chain roller 2 c can be engaged between thefirst tooth 232 a and thesecond tooth 232 b (refer toFIGS. 1 and 5 ). As shown inFIG. 8 , each of thefirst tooth 232 a and thesecond tooth 232 b comprises adrive surface 233 and anon-drive surface 234. - Since this configuration is substantially the same in the
first tooth 232 a and thesecond tooth 232 b, here, a description will be given using thefirst teeth 232 a. - Each of the
first tooth 232 a and thesecond tooth 232 b comprises afront surface 20 a, a back surface (not shown), adrive surface 233 and anon-drive surface 234. Theback surface 20 b is a surface on the opposite side of thefront surface 20 a in the axial direction of the rotational center axis X (the direction inFIG. 8 perpendicular to the paper surface). - The
drive surface 233 is a surface that couples thefront surface 20 a and the back surface in the axial direction, to a downstream side in the forward rotation direction R. Thedrive surface 233 comprises a contact point CP and afirst extension portion 233 a (an example of a drive surface extension portion). The contact point CP is where thechain roller 2 c comes into contact. Specifically, the contact point CP is where thechain roller 2 c comes into contact with thedrive surface 233 at the time of driving. - The
first extension portion 233 a is formed integrally with thedrive surface 233. Thefirst extension portion 233 a extends in the circumferential direction radially outward from the contact point CP. Specifically, thefirst extension portion 233 a protrudes towards the downstream side in the forward rotation direction R, radially outward from the contact portion CP. - The
non-drive surface 234 is a surface that couples thefront surface 20 a and the back surface in the axial direction, to an upstream side in the forward rotation direction R. For example, thenon-drive surface 234 is formed in line symmetry with thedrive surface 233 with respect to a straight line CL that connects the rotational center axis X and the center position of thefirst tooth 232 a (second tooth 232 b) in the circumferential direction. Thenon-drive surface 234 can be formed unsymmetrically relative to thedrive surface 233 with respect to the straight line CL that connects the rotational center axis X and the center position of thefirst tooth 232 a (second tooth 232 b) in the circumferential direction. - The
non-drive surface 234 comprises asecond extension portion 234 a (an example of a non-drive surface extension portion). The radially outward movement of thechain roller 2 c is suppressed by thesecond extension portion 234 a. Thesecond extension portion 234 a is formed integrally with thenon-drive surface 234. Here, since thenon-drive surface 234 is formed in line symmetry with thedrive surface 233, thesecond extension portion 234 a extends to the opposite side of thefirst extension portion 233 a in the circumferential direction. That is, thesecond extension portion 234 a extends in a circumferential direction, for example, toward the upstream side in the forward rotation direction R. - Accordingly, the drive force of the
first sprocket 14 can by reliably transmitted to thechain roller 2 c, that is, thechain 2, by thedrive surface 233. Further, the radially outward movement of thechain roller 2 c can be reliably suppressed by thedrive surface 233 and thenon-drive surface 234. - Here, a case was shown as an example in which each of the
first tooth 232 a and thesecond tooth 232 b comprises thedrive surface 233 and thenon-drive surface 234. Instead of this, the configuration can be such that only thefirst tooth 232 a, or only thesecond tooth 232 b comprise adrive surface 233 and anon-drive surface 234. Further, thefirst tooth 232 a and/or thesecond tooth 232 b can be configured to comprise only adrive surface 233, or only anon-drive surface 234. - (d) In the first and second embodiments, an example in which the
front sprocket crankshaft 19 via thecrank arm 12 was shown. Instead of this, thefront sprockets front sprocket 14 can be used, where thefront sprocket 14 moves along the crankshaft 19 (rotational center axis X) such as in the case of the front sprocket of the bicycle crank assembly that is disclosed in U.S. Patent Application Publication No. 2015/0274253A1. - (e) An outline of the
front sprockets second tooth 32 b and thefourth tooth 42 b are formed by press working, such as forging. - (f) In the first and second embodiments described above, an example in which the
first tooth third tooth 42 a or 142 a are formed in a substantially + shape was shown, but the present invention is not limited thereto. For example, at least a portion of thefirst tooth 32 a and thethird tooth 42 a can be of another shape, such as a rhombic shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape. - As shown in
FIG. 10 ,first tooth 332 a and/orthird tooth 342 a are preferably of an octagonal shape, as seen from the radial direction of the bicycle sprocket to minimize interference between thefirst tooth 332 a and/or thethird tooth 342 a and theinner link plates 2 b. In this case, excessive interference between thefirst tooth 332 a and/or thethird tooth 342 a and theinner link plates 2 b can be avoided, and a tooth-shape for securely holding theouter link plates 2 a can be easily formed by press working, such as forging. - Here, an octagonal shape is not limited to a regular octagon shape, and may be any shape that has eight sides. Further, the eight sides that constitute the octagon are not limited to straight lines, and may be curved lines having a gentle curvature.
- Specifically, as shown in
FIGS. 9 and 10 , when thefirst tooth 332 a and thethird tooth 342 a are of the octagonal shape described above, thefirst tooth 332 a and thethird tooth 342 a comprise afirst surface 352 a, asecond surface 352 b, athird surface 352 c and aninclined portion 353. - The
first surface 352 a is a surface of thefirst tooth 332 a on thefirst side surface 14 a side of thefirst sprocket 14, and a surface of thethird tooth 342 a on thethird side surface 16 a of thesecond sprocket 16. - The
second surface 352 b is a surface of thefirst teeth 332 a on thesecond side surface 14 b of thefirst sprocket 14, and a surface of thethird tooth 342 a on thefourth side surface 16 b of thesecond sprocket 16. - The
third surface 352 c extends in the circumferential direction between the axial directions of thefirst surface 352 a and thesecond surface 352 b. Thethird surface 352 c comprises adrive surface 352 d, anon-drive surface 352 e and adistal end surface 352 f that couples thedrive surface 352 d and thenon-drive surface 352 e in the circumferential direction. Theinclined portion 353 is configured to minimize (avoid excessive) interference with theinner link plates 2 b. Theinclined portion 353 comprises a firstchamfered surface 353 a, a secondchamfered surface 353 b, a thirdchamfered surface 353 c and a fourthchamfered surface 353 d. - The first
chamfered surface 353 a is formed to extend from thefirst surface 352 a to thethird surface 352 c on the drive side. The secondchamfered surface 353 b is formed to extend from thesecond surface 352 b to thethird surface 352 c on the drive side. The thirdchamfered surface 353 c is formed to extend from thefirst surface 352 a to thethird surface 352 c on the non-drive side. The fourthchamfered surface 353 d is formed to extend from thesecond surface 352 b to thethird surface 352 c on the non-drive side. - In other words, the first
chamfered surface 353 a is formed in a corner portion formed by thefirst surface 352 a and thethird surface 352 c on the drive side. The secondchamfered surface 353 b is formed in corner portions formed by thesecond surface 352 b and thethird surface 352 c on the drive side. The thirdchamfered surface 353 c is formed in corner portions formed by thefirst surface 352 a and thethird surface 352 c on the non-drive side. The fourthchamfered surface 353 d is formed in corner portions formed by thesecond surface 352 b and thethird surface 352 c on the non-drive side. - Here, the
first tooth 332 a and thethird tooth 342 a on the drive side, compared to the non-drive side, tend to more excessively interfere with theinner link plates 2 b. Therefore, the firstchamfered surface 353 a and the secondchamfered surface 353 b, which are formed on the drive side, preferably have a larger area compared to the thirdchamfered surface 353 c and the fourthchamfered surface 353 d, which are formed on the non-drive side. - Excessive interference of the
first tooth 332 a and thethird tooth 342 a with theinner link plates 2 b can be avoided by the first through fourthchamfered surfaces chamfered surfaces - Further, when the
first tooth 332 a and thethird tooth 342 a have an octagonal shape, a first axial direction contact width L3 of where the drive surface of thefirst tooth 332 a and thethird tooth 342 a make contact with thechain roller 2 c is preferably formed to be of substantially the same length as a second axial direction contact width L4 of where the drive surface of thesecond tooth 332 b and thefourth tooth 342 b make contact with thechain roller 2 c. - (g) In the first and second embodiments described above, an example in which the
first tooth first tooth 32 a can be of another shape, such as a rhombic shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape. - (h) In the first and second embodiments described above, each of the
first shift regions 34 comprises one of thesecond protrusions 36 b, but thesecond protrusions 36 b do not have to be provided. - (i) In the first and second embodiments described above, the number of the plurality of
sprocket attaching arms 24 is four, but the number of the sprocket attaching arms is not limited to four. - (j) In the first and second embodiments described above, the
first sprocket 14 can comprise a − (minus sign) shapedsecond tooth 32 b in thefirst shift regions 34, and thesecond sprocket 16 can comprise a − (minus sign) shapedfourth tooth 42 b in thesecond shift regions 44. - (k) In the second embodiment described above, an example was shown in which the additional portion of the
first tooth 32 a is made of metal, but the additional portion may be non-metallic. For example, when the additional portion is non-metallic, this additional portion is attached to the first tooth by bonding or integral molding. In this case, the noise caused during pedaling caused by contact between the chain and the sprocket teeth making can be reduced. - (l) At least one of the
first tooth second tooth 32 b or 132 b of the bicycle sprocket of the present invention can preferably comprise a plated layer. - For example, when the
first teeth second teeth 32 b or 132 b are made of aluminum, the plated layer is preferably a nickel plated layer, for the purpose of wear resistance. Further, when thefirst teeth second teeth 32 b or 132 b are made of iron, the plated layer is preferably a nickel chrome plated layer, for the purpose of rust resistance. - Meanwhile, when the
first tooth second tooth 32 b or 132 b are made of iron, thetooth teeth second tooth 32 b or 132 b, preferably comprise an electrodeposition coating layer, for the purpose of rust resistance and coloring. - (m) In the first and second embodiments described above, an example was shown in which the
first sprocket 14 is configured to form thefirst sprocket body 30 made of synthetic resin, the firstannular portion 31 and thefirst tooth portion 32 b made of metal. - Alternatively, the
first sprocket 14 can be configured from metal, and thefirst sprocket body 30, the firstannular portion 31, and thefirst tooth portion 32 b can be integrally molded. In this case, thefirst sprocket body 30, the firstannular portion 31, and thefirst tooth portion 32 b are formed of metal, such as aluminum, titanium, or iron/stainless steel. - An example of the
first sprocket 314 configured in this way is shown inFIG. 11 . The configuration inFIG. 11 is substantially the same as the first and second embodiments described above, and the typical configurations are given the same reference symbols as the first embodiment. - (n) Instead of the
first sprocket first sprocket 214 can be configured as shown inFIGS. 12A and 12B . Meanwhile, inFIGS. 12A and 12B , configurations that are substantially the same as the first and second embodiments described above are given the same reference symbols as the first embodiment. - In the
first sprocket 214, a first through-hole 130 a is provided to thefirst sprocket body 30. Further, a second through-hole 130 b is provided to the firstannular portion 31. Aring member 130 c, such as a washer, is disposed in the first through-hole 130 a. Specifically, thefirst sprocket body 30 is integrally molded with the firstannular portion 31 and thering member 130 c, so that the inner perimeter surface of thering member 130 c is substantially flush with the inner perimeter surface of the second through-hole 130 b. - When the
first sprocket 214 is configured in this way, one of the first fixingbolts 26 is inserted into each of thering members 130 c, each of the second through-holes 130 b, and each of the first attachingportions 24 a, and is then screwed to a nut member (not shown). With this, thefirst sprocket body 30 is fixed to thesprocket attaching arms 24. - (o) In the first and second embodiments described above, an example was shown in which the
second tooth 32 b of thefirst sprocket 14 are formed by press working, such as forging, together with thefirst recess 32 e. Instead of this, as shown in part (A) ofFIG. 13 -part (D) ofFIG. 13 , thesecond tooth 32 b can be formed by press working (such as forging) and a cutting process. In part (A) ofFIG. 13 -part (D) ofFIG. 13 , each step is schematically represented for ease of description. - In this case, the
second tooth 32 b are formed by a first pressing step (refer to part (B) ofFIG. 13 ), a cutting step (refer to part (C) ofFIG. 13 ) after the first pressing step, and a second pressing step (refer to part (D) ofFIG. 13 ) after the cutting step. - As shown in part (D) of
FIG. 13 , thesecond tooth 32 b comprise afifth surface 52 a (an example of a first surface) and asixth surface 52 b (an example of a first surface). For example, thefifth surface 52 a is formed on thesecond tooth 32 a, on thefirst side surface 14 a (refer toFIG. 2 ) of thefirst sprocket 14. Thesixth surface 52 b is a surface that is located on the opposite side of thefifth surface 52 a in an axial direction parallel to the rotational center axis X. For example, thesixth surface 52 b is formed on thesecond tooth 32 b, on thesecond side surface 14 b (refer toFIG. 4 ) of thefirst sprocket 14. - Specifically, as shown in part (A) of
FIG. 13 , in the initial state, the surface on which thefifth surface 52 a of thesecond tooth 32 b is formed (first pressingportion 152 a described below) and the surface on which thesixth surface 52 b is formed (secondpressing portion 152 c described below) are formed on substantially the same surface as the outer surface of the firstannular portion 31 of thefirst sprocket 14. - A first pressing step is a process for pressing the
fifth surface 52 a of thesecond tooth 32 b. As shown in part (B) ofFIG. 13 , in the first pressing step, with the firstannular portion 31 in a fixed state, thefifth surface 52 a of thesecond tooth 32 b is pressed by a pressing member A of a pressing device (not shown). - Here, the first
pressing portion 152 a where the pressing member A presses, is the portion where thesecond tooth 32 b and thefirst recess 32 e are formed. In this way, when the pressing member A presses the firstpressing portion 152 a, thefifth surface 52 a of thesecond tooth portion 32 b is formed, and a portion on thesixth surface 52 b protrudes, which is located substantially on the opposite side of the firstpressing portion 152 a. Hereinafter, this portion will be referred to as theprotrusion 152 b. - The cutting step is a process for cutting the
protrusion 152 b, which protrudes in the axial direction due to the first pressing step, on thesixth surface 52 b of thesecond tooth 32 b. As shown in part (C) ofFIG. 13 , in the cutting step, theprotrusion 152 b formed on thesixth surface 52 b is cut by a cutting device B. Specifically, theprotrusion 152 b is cut by the cutting device B so that the surface remaining after cutting is substantially the same surface as the outer surface of the firstannular portion 31. - A second pressing step is a step for pressing the
sixth surface 52 b side of thesecond tooth 32 b. As shown in part (D) ofFIG. 13 , in the second pressing step, in a state in which a mold D for forming the outer shape of thesecond tooth 32 b is abutting the firstpressing portion 152 a, thesixth surface 52 b side of thesecond tooth 32 b is pressed by a pressing member C of the pressing device. - Here, the second
pressing portion 152 c where the pressing member C presses, is the portion where thetooth teeth 32 b and thefirst recess 32 e are formed. In this way, when the pressing member C presses the secondpressing portion 152 c, thesixth surface 52 b of thesecond tooth portion 32 b is formed. Further, the teeth edge 52 c of thesecond tooth portion 32 b as well as thefifth surface 52 a and thesixth surface 52 b are formed. - As described above, the
second tooth 32 b can be formed by using the first pressing step, the cutting step and the second pressing step. Meanwhile, after thesecond tooth 32 b are formed in the above way, a polishing step for adjusting the shape of thesecond tooth 32 b, and a plating step (preferably, a nickel plating process) for improving the wear resistance of thesecond tooth 32 b can be added selectively. - Here, an example was shown in which the
second tooth 32 b are formed by press working and a cutting process, but thefourth tooth 42 b of thesecond sprocket 16 can be formed in the same way as well. - (p) In the first and second embodiments and the other embodiments described above,
front sprockets - The present invention can be widely applied to bicycle sprockets and bicycle sprocket assemblies.
- In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts unless otherwise stated.
- Also, it will be understood that although the terms “first” and “second” may be used herein to describe various components these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, for example, a first component discussed above could be termed a second component and vice versa without departing from the teachings of the present invention. The term “attached” or “attaching”, as used herein, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to the intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e. one element is essentially part of the other element. This definition also applies to words of similar meaning, for example, “joined”, “connected”, “coupled”, “mounted”, “bonded”, “fixed” and their derivatives. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean an amount of deviation of the modified term such that the end result is not significantly changed.
- While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, unless specifically stated otherwise, the size, shape, location or orientation of the various components can be changed as needed and/or desired so long as the changes do not substantially affect their intended function. Unless specifically stated otherwise, components that are shown directly connected or contacting each other can have intermediate structures disposed between them so long as the changes do not substantially affect their intended function. The functions of one element can be performed by two, and vice versa unless specifically stated otherwise. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Claims (9)
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US16/455,507 US11203395B2 (en) | 2015-10-09 | 2019-06-27 | Bicycle sprocket and bicycle sprocket assembly |
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US16/455,507 US11203395B2 (en) | 2015-10-09 | 2019-06-27 | Bicycle sprocket and bicycle sprocket assembly |
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US11339865B2 (en) | 2017-05-12 | 2022-05-24 | MIRANDA & IRMAO, LDa | Narrow—wide teeth chainring |
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US9581229B2 (en) * | 2014-02-10 | 2017-02-28 | Wolf Tooth Components, LLC | Sprocket |
US9625027B2 (en) * | 2014-04-08 | 2017-04-18 | Wolf Tooth Components, LLC | Sprocket |
US9581231B2 (en) * | 2014-04-08 | 2017-02-28 | Wolf Tooth Components, LLC | Sprocket |
US9404565B2 (en) * | 2014-04-08 | 2016-08-02 | Wolf Tooth Components, LLC | Sprocket |
US9409624B2 (en) * | 2014-04-11 | 2016-08-09 | Shimano Inc. | Bicycle sprocket |
US9964196B2 (en) * | 2014-05-20 | 2018-05-08 | Shimano Inc. | Bicycle sprocket |
-
2016
- 2016-07-25 US US15/218,677 patent/US20170101159A1/en not_active Abandoned
- 2016-09-06 CN CN201610804109.XA patent/CN106564558B/en active Active
- 2016-09-06 CN CN201910503701.XA patent/CN110371235B/en active Active
- 2016-10-07 DE DE102016219453.4A patent/DE102016219453A1/en active Pending
-
2019
- 2019-06-27 US US16/455,507 patent/US11203395B2/en active Active
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11339865B2 (en) | 2017-05-12 | 2022-05-24 | MIRANDA & IRMAO, LDa | Narrow—wide teeth chainring |
US11396937B2 (en) | 2017-05-12 | 2022-07-26 | MIRANDA & IRMAO, LDa | Chainring |
US11739823B2 (en) | 2017-05-12 | 2023-08-29 | MIRANDA & IRMAO, LDa | Narrow—wide teeth chainring |
Also Published As
Publication number | Publication date |
---|---|
CN110371235B (en) | 2021-02-05 |
US20170101159A1 (en) | 2017-04-13 |
CN110371235A (en) | 2019-10-25 |
DE102016219453A1 (en) | 2017-04-13 |
CN106564558B (en) | 2020-11-13 |
CN106564558A (en) | 2017-04-19 |
US11203395B2 (en) | 2021-12-21 |
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